This invention relates generally to wheel assemblies, and especially to wheel assemblies which are employed in ground-engaging drive systems which are used in e.g. tracked vehicles and in endless belt conveyors. While the disclosure herein focuses on tracked vehicles and endless track drive systems for such vehicles, it will be understood that the invention can be employed in other endless track drive systems.
Ground-engaging endless track drive systems in tracked vehicles employ a plurality of wheel assemblies to define a track path, which path is beneficially traversed by the track in causing the vehicle to move along the ground. Such track drive systems can include, for example and without limitation, on each side of the vehicle, a drive wheel assembly disposed adjacent e.g. the rear of the vehicle, an idler wheel assembly disposed adjacent e.g. the front of the vehicle, and one or more mid-roller wheel assemblies backing up the ground-engaging surface of the track between the drive wheel assembly and the idler wheel assembly.
In some embodiments, such track systems employ, as an additional element, one or more separate and distinct tensioning wheel assemblies in e.g. an upper portion of the track path. In other embodiments, the tensioning function is integrated into the operation of one or more of the other wheel assemblies, as a secondary function in addition to the primary function of the respective wheel assembly.
The structures of the several wheel assemblies are typically designed and configured according to the specific uses for which each such wheel assembly is to be employed. Accordingly, drive wheel assemblies are structured for their driving function.
Idler wheel assemblies are structured for their function of performing a significant angle turn of the track, and typically are structured to perform or assist with functions related to steering the direction of movement of the vehicle. Since the idler wheel assembly generally does not bear the stresses of driving the vehicle, on a given vehicle, the idler wheel assemblies are typically less complex, and may be less robust, than the drive wheel assemblies.
Mid-roller wheel assemblies are structured and mounted to provide downwardly-directed support of the underlying track, and thus can be spring loaded from the frame for such support of the endless track. Mid-roller wheel assemblies generally do not perform driving or steering functions.
Similarly, tensioning wheel assemblies, not shown in the drawings, are structured for typically upwardly-directed support of the track, and thus are also typically designed to be spring loaded from the frame. As with mid-roller wheel assemblies, tensioning wheel assemblies generally do not perform driving or steering functions.
Thus, while the drive wheel assemblies and the idler wheel assemblies, which perform driving and steering functions, are typically relatively more robust, and can be more complex, mid-roller wheel assemblies and tensioning wheel assemblies typically perform less demanding functions and thus can be somewhat less robust and may be simpler in design.
Wheel assemblies used in track drive systems typically employ an outer layer of elastomeric material, such as rubber, as an outer driving surface. Such elastomeric layer is resilient, thus providing at least some cushioning of the vehicle frame from the rough terrain over which such vehicles may be operated. In addition, the rubber outer surface generates less noise against the track than does a metal outer surface of the wheel assembly. Yet further, the elastomeric, e.g. rubber, outer surface of the wheel assembly has a higher coefficient of friction than commonly available metal, whereby friction driving of the track is facilitated.
The elastomeric layer of the wheel assembly is typically mounted to a metal wheel, which is mounted to a wheel hub, the hub being mounted to a respective axle or other mounting shaft. Various structures have been proposed for such mounting of the elastomeric layer to the wheel. There are available, for example, as conventional structures, entrapping flanges integral with the wheel wherein the flanges extend outwardly of, and partially overlie, the outer surface of the elastomeric layer, such that the flanges interfere with interface of the elastomeric surface with a track having an inner surface which is generally flat when taken across the transverse dimension of the track.
Another conventional structure includes a coiled metal spring as an outer track-engaging surface of the wheel assembly, held in place by a separate side flange which extends upwardly above the track-engaging outer surface of the wheel assembly.
Yet another conventional structure teaches spacer sleeves extending through, and apparently molded into, the elastomeric tire material and receiving bolts which extend between retaining rings on opposing sides of the tire, and wheel, through the spacer sleeves, thereby to hold the tire to the wheel.
All the above structures are quite complex, including associated cost, both of manufacturing such structures and of maintaining such structures.
In a known simpler design, for mid-roller wheel assemblies, a non-pneumatic rubber tire is adhesively mounted to an outer surface of a wheel, thereby to provide a relatively low cost wheel assembly. The wheel has an outer surface which receives the inner surface of the tire. Such adhesively-mounted tire can separate from the wheel under the severe operating conditions in which such vehicles are commonly used; and such separation requires replacement of both the tire and the hub.
It is an object of this invention to provide a relatively less complex wheel assembly wherein a relatively less complex elastomeric tire is mounted to a generally less complex wheel.
It is another object to provide such wheel assembly wherein the tire can be replaced without replacing the wheel.
It is still another object to provide such wheel assembly wherein the tire is held on the wheel by a side flange mounted to the wheel, and wherein no portion of the mounting structure passes through the tire so as to require an aperture extending transversely through the tire, outside the inner surface of the tire.
Still another object is to provide such wheel assembly wherein tire defines the entirety of the width of the outer surface of the wheel assembly.
This invention contemplates a wheel assembly for use in an endless track drive system. The wheel assembly comprises a tire comprising a tire body. The tire body comprises elastomeric material composition. Structurally, the tire body comprises a tire exterior. The tire exterior comprises an inner surface, an outer surface, first and second respective side surfaces extending generally from the outer surface toward the inner surface, and first and second recesses in the exterior of the tire body between the inner surface and respective ones of the side surfaces. The first and second recesses each define a side-facing recess surface thereof. The tire body further comprises a plurality of cables proximate the inner surface of the tire body, embedded in and surrounded by the elastomeric material, the cables in combination limiting radial stretching of the tire.
The wheel assembly further comprises a wheel having an inner flange defining a central opening for mounting the wheel to an axle through a wheel hub, for rotation of the wheel and hub with respect to such axle, and an outer flange having first and second opposing sides, and an outer surface corresponding to an outer surface of the wheel. The outer surface of the wheel receives the inner surface of the tire thereon at a wheel-tire interface. The inner surface of the tire and the outer surface of the wheel are cooperatively sized and configured such that the tire can be mounted on the wheel with a snug fit. The outer surface of the outer flange comprises a first lesser diameter portion extending from the first side of the wheel toward the second opposing side, along at least 60 percent, preferably at least 70 percent, more preferably at least 80 percent, of the width of the wheel between the first and second side edges. The lesser diameter surface portion has a first lesser diameter. The outer surface of the wheel further comprises a second greater diameter portion, which comprises a first side flange at the second side, integral with the outer flange of the wheel. The first side flange has a second diameter greater than the first diameter, and comprises a first abutment surface facing toward a center of the outer surface and abutting the side-facing recess surface of the first recess in the tire. A web connects the inner flange of the wheel to the outer flange of the wheel.
As a separate and distinct element, the wheel assembly comprises a second side flange disposed against the second side of the outer flange of the wheel. A second abutment surface on the second side flange faces toward the center of the outer surface of the outer flange. The second side flange is removably mounted to the outer flange of the wheel by fasteners. The second abutment surface abuts the side-facing recess surface of the second recess in the exterior of the tire.
The difference between the magnitudes of the first and second diameters is greater than the radial stretch capability of the combination of the cables and the elastomeric material forming the tire, thereby to prevent transverse movement of the tire off the wheel while the second side flange is mounted to the wheel.
In preferred embodiments, the cables are steel cables.
Also in preferred embodiments, the outer surface of the tire defines the entirety of an outer surface of the wheel assembly.
Further to preferred embodiments, the tire is free from fasteners passing therethrough for affixation of the tire to the wheel.
Still further to preferred embodiments, the wheel assembly is free from adhesive at the wheel-tire interface.
Yet further to preferred embodiments, the second side flange comprises an annular body having apertures therein, receiving fasteners removably affixing the annular body to the first side of the outer flange, and an annular top leg extending from the annular body toward a central portion of the outer surface of the outer flange, between the outer surface of the outer flange and the inner surface of the elastomeric tire at the second recess. The fasteners preferably extend through the apertures in the second side flange and into preferably blind apertures in the side of the outer flange of the wheel.
In preferred embodiments, the outer flange has a relatively greater first width between a center-line, extending through and centered along the wheel web perpendicular to the lesser diameter portion, and the second side edge at the first side flange, and a relatively lesser second width between the center-line and the first side edge.
Yet in preferred embodiments, the combination of the second width of the outer flange, plus a width of the second side flange, is approximately equal to the first width.
Preferred material for the elastomeric material in the tire comprises a rubber compound.
In preferred embodiments, the first and second abutment surfaces form angles xe2x80x9cxcex1xe2x80x9d, with the lesser diameter portion of the outer surface of the outer flange of no more than about 135 degrees. A leg of each such angle xe2x80x9cxcex1xe2x80x9d is disposed between the respective abutment surface and the center of the outer surface of the outer flange.
The invention further comprises an endless track drive system, comprising a prime mover such as an internal combustion engine or an electric motor, an endless track mounted about a plurality of wheel assemblies defining a path therefore, and a drive train transferring drive power from the prime mover to at least one of the wheel assemblies, at least one of the plurality of wheel assemblies comprising a wheel assembly as described above.
The invention also contemplates a tracked vehicle comprising a frame, a prime mover, a track assembly, and a drive train transferring drive power from the prime mover to the track assembly, the track assembly comprising an endless track and a plurality of wheel assemblies about which the endless track is mounted, including at least one of the wheel assemblies as described above.
Wheel assemblies of the invention are preferably used as mid-wheel rollers, idler wheel assemblies, and/or tensioning wheel assemblies.